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Electrical Stimulation of Artificial Heart Muscle: A Look Into the Electrophysiologic and Genetic Implications.

ABSTRACT: Development of tissue-engineered hearts for treatment of myocardial infarction or biologic pacemakers has been hindered by the production of mostly arrhythmic or in-synergistic constructs. Electrical stimulation (ES) of these constructs has been shown to produce tissues with greater twitch force and better adrenergic response. To further our understanding of the mechanisms underlying the effect of ES, we fabricated a bioreactor capable of delivering continuous or intermittent waveforms of various types to multiple constructs simultaneously. In this study, we examined the effect of an intermittent biphasic square wave on our artificial heart muscle (AHM) composed of neonatal rat cardiac cells and fibrin gel. Twitch forces, spontaneous contraction rates, biopotentials, gene expression profiles, and histologic observations were examined for the ES protocol over a 12 day culture period. We demonstrate improved consistency between samples for twitch force and contraction rate, and higher normalized twitch force amplitudes for electrically stimulated AHMs. Improvements in electrophysiology within the AHM were noted by higher conduction velocities and lower latency in electrical response for electrically stimulated AHMs. Genes expressing key electrophysiologic and structural markers peaked at days 6 and 8 of culture, only a few days after the initiation of ES. These results may be used for optimization strategies to establish protocols for producing AHMs capable of replacing damaged heart tissue in either a contractile or electrophysiologic capacity. Optimized AHMs can lead to alternative treatments to heart failure and alleviate the limited donor supply crisis.

SUBMITTER: Mohamed MA

PROVIDER: S-EPMC5469367 | biostudies-literature | 2017 May/Jun

REPOSITORIES: biostudies-literature

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Electrical Stimulation of Artificial Heart Muscle: A Look Into the Electrophysiologic and Genetic Implications.

Mohamed Mohamed A MA Islas Jose F JF Schwartz Robert J RJ Birla Ravi K RK

ASAIO journal (American Society for Artificial Internal Organs : 1992) 20170501 3

Development of tissue-engineered hearts for treatment of myocardial infarction or biologic pacemakers has been hindered by the production of mostly arrhythmic or in-synergistic constructs. Electrical stimulation (ES) of these constructs has been shown to produce tissues with greater twitch force and better adrenergic response. To further our understanding of the mechanisms underlying the effect of ES, we fabricated a bioreactor capable of delivering continuous or intermittent waveforms of variou ...[more]

PMID: 28459744

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Project description:Stimulation of the mouse hindlimb via the sciatic nerve was used to induce contractions for 4 hours to investigate acute muscle gene activation in a model of muscle phenotype conversion. Initial force production (1.6 + 0.1 g/g body weight) declined 45% within 10 min and was maintained for the remainder of the experiment. Force returned to initial levels upon completion of the study. An immediate-early growth response was present in the EDL (FOS, JUN, ATF3, MAFK) with a similar but attenuated pattern in the soleus. Transcript profiles showed decreased fast fiber specific mRNA (myosin heavy chains 2A, 2B; troponins T3, I; -tropomyosin, m-creatine kinase) and increased slow transcripts (myosin heavy chain slow/1, troponin C, tropomyosin 3) in the EDL. Histological analysis of the EDL revealed glycogen depletion without inflammatory cell infiltration or myofiber damage in stimulated vs. control muscles. Several fiber type specific transcription factors (EYA1, TEAD1, NFATc1 and c4, PPARG, PPARGC1 and β, BHLHB2) increased in the EDL along with transcription factors characteristic of embryogenesis (KLF4, SOX17, TCF15, PKNOX1, ELAV). No established in vivo satellite cell markers or the genes activated during our parallel studies of satellite cell proliferation in vitro (CYCLINS A2, B2, C, E1, MyoD) increased in the stimulated muscles. These data indicated that onset of fast to slow phenotype conversion occurred in the EDL within 4 hours of stimulation without satellite cell recruitment or muscle injury but was driven by phenotype specific transcription factors from resident fiber myonuclei including activation of nascent developmental transcriptional programs. Adult male Swiss Webster mice (30-35 g) were anesthetized, a bipolar electrode was implanted adjacent to the sciatic nerve and the hindlimb immobilized. The voltage-force relation was determined to establish supramaximal stimulation conditions and the length-tension relation was determined to set the resting length for maximum twitch tension. Contractions were induced by sciatic nerve stimulation (0.5 msec duration, 2-5 volts). The muscles were allowed to rest 15 minutes for full metabolic recovery at physiologic temperatures. Supramaximal stimulation was applied at a rate of 10 Hz for 4 hours. At the end of each experiment the soleus muscles were carefully dissected and flash frozen in liquid nitrogen for analysis of mRNA expression via microarray analysis. The contralateral, unstimulated Soleus provided a genetically matched, paired control for each specimen.

Project description:ObjectivesLow-frequency electrical muscle stimulation (LF-EMS) may have the potential to reduce breathlessness and increase exercise capacity in the chronic heart failure population who struggle to adhere to conventional exercise. The study's aim was to establish if a randomised controlled trial of LF-EMS was feasible.Design and settingDouble blind (participants, outcome assessors), randomised study in a secondary care outpatient cardiac rehabilitation programme.ParticipantsPatients with severe heart failure (New York Heart Association class III-IV) having left ventricular ejection fraction <40% documented by echocardiography were eligible.InterventionsParticipants were randomised (remotely by computer) to 8 weeks (5×60 mins per week) of either LF-EMS intervention (4 Hz, continuous, n=30) or sham placebo (skin level stimulation only, n=30) of the quadriceps and hamstrings muscles. Participants used the LF-EMS straps at home and were supervised weekly OUTCOME MEASURES: Recruitment, adherence and tolerability to the intervention were measured during the trial as well as physiological outcomes (primary outcome: 6 min walk, secondary outcomes: quadriceps strength, quality of life and physical activity).ResultsSixty of 171 eligible participants (35.08%) were recruited to the trial. 12 (20%) of the 60 patients (4 LF-EMS and 8 sham) withdrew. Forty-one patients (68.3%), adhered to the protocol for at least 70% of the sessions. The physiological measures indicated no significant differences between groups in 6 min walk distance(p=0.13) and quality of life (p=0.55) although both outcomes improved more with LF-EMS.ConclusionPatients with severe heart failure can be recruited to and tolerate LF-EMS studies. A larger randomised controlled trial (RCT) in the advanced heart failure population is technically feasible, although adherence to follow-up would be challenging. The preliminary improvements in exercise capacity and quality of life were minimal and this should be considered if planning a larger trial.Trial registration numberISRCTN16749049.

Project description:PurposeMacrophage accumulation in response to decreasing myonuclei may be the major mechanism underlying immobilization-induced muscle fibrosis in muscle contracture, an intervention strategy suppressing these lesions is necessary. Therefore, this research investigated the effect of belt electrode-skeletal muscle electrical stimulation (B-SES), a new electrical stimulation device, to the macrophage accumulation via myonuclei decrease in immobilization-induced muscle fibrosis.Materials and methods18 Wistar male rats were divided into the control group, immobilization group (with plaster cast fixation to immobilize the soleus muscles in a shortened position for 2 weeks), and B-SES group (with muscle contractile exercise through B-SES during the immobilization period). B-SES stimulation was performed at a frequency of 50 Hz and an intensity of 4.7 mA, muscle contractile exercise by B-SES was applied to the lower limb muscles for 20 minutes/session (twice a day) for 2 weeks (6 times/week). The bilateral soleus muscles were used for histological, immunohistochemical, biochemical, and molecular biological analyses.ResultsThe number of myonuclei was significantly higher in the B-SES group than in the immobilization group, and there was no significant difference between the B-SES and control groups. The cross-sectional area of type I and II myofibers in the immobilization and B-SES groups was significantly lower than that in the control group, and the cross-sectional area of type I myofibers in the B-SES group was higher than that in the immobilization group. However, Atrogin-1 and MuRF-1 mRNA expression in the immobilization and B-SES groups was significantly higher than those in the control group. Additionally, the number of macrophages, IL-1β, TGF-β1, and α-SMA mRNA expression, and hydroxyproline expression was significantly lower in the control and B-SES groups than those in the immobilization group.ConclusionThis research surmised that muscle contractile exercise through B-SES prevented immobilization-induced muscle fibrosis, and this alteration suppressed the development of muscle contracture.

Project description:IntroductionCritically ill patients are characterized by increased loss of muscle mass, partially attributed to sepsis and multiple organ failure, as well as immobilization. Recent studies have shown that electrical muscle stimulation (EMS) may be an alternative to active exercise in chronic obstructive pulmonary disease (COPD) and chronic heart failure (CHF) patients with myopathy. The aim of our study was to investigate the EMS effects on muscle mass preservation of critically ill patients with the use of ultrasonography (US).MethodsForty-nine critically ill patients (age: 59 +/- 21 years) with an APACHE II admission score >or=13 were randomly assigned after stratification upon admission to receive daily EMS sessions of both lower extremities (EMS-group) or to the control group (control group). Muscle mass was evaluated with US, by measuring the cross sectional diameter (CSD) of the vastus intermedius and the rectus femoris of the quadriceps muscle.ResultsTwenty-six patients were finally evaluated. Right rectus femoris and right vastus intermedius CSD decreased in both groups (EMS group: from 1.42 +/- 0.48 to 1.31 +/- 0.45 cm, P = 0.001 control group: from 1.59 +/- 0.53 to 1.37 +/- 0.5 cm, P = 0.002; EMS group: from 0.91 +/- 0.39 to 0.81 +/- 0.38 cm, P = 0.001 control group: from 1.40 +/- 0.64 to 1.11 +/- 0.56 cm, P = 0.004, respectively). However, the CSD of the right rectus femoris decreased significantly less in the EMS group (-0.11 +/- 0.06 cm, -8 +/- 3.9%) as compared to the control group (-0.21 +/- 0.10 cm, -13.9 +/- 6.4%; P < 0.05) and the CSD of the right vastus intermedius decreased significantly less in the EMS group (-0.10 +/- 0.05 cm, -12.5 +/- 7.4%) as compared to the control group (-0.29 +/- 0.28 cm, -21.5 +/- 15.3%; P < 0.05).ConclusionsEMS is well tolerated and seems to preserve the muscle mass of critically ill patients. The potential use of EMS as a preventive and rehabilitation tool in ICU patients with polyneuromyopathy needs to be further investigated.Trial registrationclinicaltrials.gov: NCT00882830.

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Electrical Stimulation of Artificial Heart Muscle: A Look Into the Electrophysiologic and Genetic Implications.

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Electrical Stimulation of Artificial Heart Muscle: A Look Into the Electrophysiologic and Genetic Implications.

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